CHROMIC ACID, C
OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
CAS: Varies with compound
The current OSHA limit for chromic acid and chromates is a ceiling limit of 0.1 mg/m3 measured as Cr03. The Agency did not propose to revise this limit. The ACGIH has established a TLV-TWA of 0.05 mg/m3 as Cr(VI) for both the soluble and insoluble forms of chromate (except zinc chromate), and has designated insoluble chromates as confirmed human carcinogens (A1). (It should be noted that the 0.05 mg/m3 limit, expressed as Cr(VI), approximates 0.01 mg/m3 measured as CrO3.) NIOSH (1975b/Ex. 1-258) has recommended that exposure to the noncarcinogenic forms of chromium (VI) be limited to 0.025 mg Cr(VI)/m3 as a 10-hour TWA and 0.05 mg Cr(VI)/m3 as a 15-minute ceiling. For the carcinogenic (i.e., insoluble) forms of chromium (VI), NIOSH recommends a 10-hour TWA limit of 0.001 mg Cr(VI)/m3.
The ACGIH recommendation for both soluble (noncarcinogenic) and insoluble (carcinogenic) forms of Cr(VI) is based largely on reports by Bloomfield and Blum (1928/Ex. 1-822) and by the Federal Security Agency of the U.S. Public Health Service (Federal Security Agency 1953, as cited in ACGIH 1986/Ex. 1-3, p. 140) that demonstrate nasal irritation and some evidence of liver enlargement and kidney dysfunction among chromate workers exposed to 0.06 to 0.07 mg Cr(VI)/m3. The ACGIH also cites a report by Mancuso and Hueper (1951/Ex. 1-215) of excess lung cancer among chromate workers exposed to 0.01 to 0.15 mg/m3 soluble chromate and 0.1 to 0.58 mg/m3 insoluble chromate. Animal data cited by the ACGIH indicate that insoluble chromate salts were likely to have been responsible for the increased incidence of cancer seen in the Mancuso and Hueper (1951/Ex. 1-215) study. The ACGIH (1986/Ex. 1-3) concluded that the 0.05 mg/m3 TLV-TWA would protect workers from chromium-induced nasal irritation and possible liver or kidney damage, and, in the case of the insoluble chromates, would provide an adequate margin of safety from respiratory cancer.
NIOSH (1975a/Ex. 1-185) cited several studies showing inflammation and ulceration of the nasal cavity at short-term exposure levels greater than 0.1 mg CrO3/m3. In its criteria document on chromic acid (NIOSH 1973e/Ex. 1-264), NIOSH recommended that the current OSHA ceiling limit (0.1 mg CrO3/m3) be supplemented with a 0.05 mg CrO3/m3 10-hour TWA limit. In its criteria document on chromium (VI), NIOSH (1975b/Ex. 1-258) reaffirmed these limits but extended their application to all forms of noncarcinogenic chromate. Thus, the 0.1 mg CrO3/m3 ceiling limit corresponds to a 0.05 mg Cr(VI)/m3 ceiling limit, and the 0.05 mg CrO3/m3 TWA limit corresponds to a 0.025 mg Cr(VI)/m3 TWA. For the carcinogenic (insoluble) forms of Cr(VI), NIOSH recommends the lowest detectable level, which is 0.001 mg Cr(VI)/m3 as a 10-hour TWA.
Zinc chromate is an insoluble, carcinogenic form of chromate. Accordingly, the current OSHA limit for chromic acid and chromates applies, as does the NIOSH limit of 0.001 mg/m3 for carcinogenic chromates. The ACGIH (1986/Ex. 1-3) reviewed several small epidemiologic studies of zinc chromate workers, all of which reported excesses of lung cancer. Because of the consistency of this evidence, the ACGIH (1986/Ex. 1-3) classified zinc chromate as a confirmed human carcinogen (A1) and reduced the TLV to 0.05 mg Cr(VI)m3.
Evaluation of the alternate recommendations is complicated by the different valence states of chromium compounds, the different methods of measurement (CrO3 or Cr(VI)), and differences in defining those substances that present a cancer hazard (soluble vs. insoluble or valence state). The 0.05 ppm TWA-TLV is less restrictive than the current 0.05 ppm ceiling limit (as Cr(VI)), and would not be considered a revised PEL. In the NPRM, OSHA proposed that the existing PEL of 0.1 mg/m3 (measured as CrO3) be maintained. In the NPRM, OSHA stated that it would consider whether to place these substances on its regulatory agenda for future consideration for Section 6(b) rulemaking, rather than making any changes as part of this rulemaking. NIOSH (Ex. 8-47, Table N6B) concurred that the chromates should be part of a separate 6(b) rulemaking, and both the AFL-CIO (Ex. 194) and the UAW (Tr. pp. 7-65 to 7-67) agreed that a comprehensive standard would be appropriate for chromates. No other comments were received on this issue. Therefore, because of the complexities of the scientific issues regarding the carcinogenicity of the various forms of chromates, OSHA is not at this time revising its current PEL for chromic acid or chromates, but will continue to evaluate the need for a separate 6(b) rulemaking for these substances.
- Page last reviewed: September 28, 2011
- Page last updated: September 28, 2011
- Content source:
- National Institute for Occupational Safety and Health Education and Information Division